Turbine blade shroud



April 16,1940. J. c. BOHAN TURBINE BLADE SHROUD 2 Sheets-She et 1 FiledSept. 14, 1938 INVENTOR I WITNESSES: j

N. R w BMW 0 m m m m mm 1% m W'YYM Q I Patented Apr. 16, 1940 UNITEDSTATES Search Room PATENT OFFICE TURBINE BLADE SHROUD PennsylvaniaApplication September 14, 1938, Serial No. 229,815

10 Claims.

The invention relates to shrouded turbine blading and it has for anobject to provide a tenon and shroud connection permitting the use of arelatively thick shroud.

Another object of the invention is the provision of a blade and shroudconnection wherein the blades are provided with cylindrical tenonsextending through openings in the shroud, which openings are ofrelatively greater diameter than the tenons with the result that,irrespective of shroud thickness and the radial disposition of theblades and their tenons, assembly of the shroud on the tenons may beaccomplished without interference.

A further object of the invention is the provision of ferrules fillingthe spaces between the tenons and the walls of the shroud openings.

Yet another object of the invention is the provision of a novelconnection between the ferrules and their associated parts.

These and other objects are effected by my invention as will be apparentfrom the following description and claims taken in connection with theaccompanying drawings, forming a part of this application, in which:

Fig. l is an exploded view, in side elevation and partly in section, ofthe invention;

Fig. 2 is a side elevational view, partly in section, showing a shroudstrip partially connected in assembled relation to its blades;

Fig. 3 is a top plan view of the structure shown in Fig. 2;

Figs. 4 to 9 are fragmentary, side elevational views, partly in section,each showing a further modification of the invention; and,

Fig. 10 is a fragmentary, side elevational view. partly in section,showing the arrangement of Figs. 1 to 3, with the projecting headsfinished ofi flush with the outer surface of the shroud.

Referring now to the drawings more in detail, in Figs. 1 to 3, there isshown, at In, an inner -supporting member or rotor element having anarcuate outer periphery Illa with a row of turbine blades ll extendingradially outward from the latter. The blades may be attached to thesupporting member ID in any well known manner.

The outer free ends of the blades are provided with radially outwardlyextending cylindrical tenons l2. The outer ends of the blades are bracedby means of a relatively thick shroud ring i3 comprised by segments I4having outwardly flaring tapered openings if: for the reception of thetenons, the openings being substantially larger than the tenons 12 toavoid interference with assembly on account of inward convergence of thetenons. In this connection. the openings l5 are so spaced that, with theinner face of the shroud strip contacting with the blade ends, the stripmay be positioned to bring the openings into coaxial relation withrespect to the tenons.

Bushings or ferrules l6 encompass the blade tenons and fit the shroudstrip openings. Accordingly, such bushings have outwardly flaringtapered walls lBa, corresponding both in size and taper to the openings[5 in the shroud segments and have inner cylindrical walls I! for thecylindrical tenons i2. the outer ends of the openings preferably beingchamfered, as at l8, to provide inwardly-converging annular spaces 19into which the tenon ends may be deformed, as by peening or spinning, toprovide heads 20 for re-- taining the shroud strips, tenons and bladesin assembled relation.

The structure disclosed in Fig. 4 differs from that just described inthat the openings in the shroud strip are cylindrical rather thanconical. and the ferrules have corresponding cylindrical outer surfacesfitting the openings and have annular ribs or lips 21 overlying andengaging the outer peripheral surface of the shroud strip 24.

The arrangement shown in Fig. 5 differs from that of the preferredembodiment, illustrated in Figs. 1 to 3. in that the ferrules 28 havethreaded connections with the shroud strip 29; and, in Fig. 6, thethreaded connections 32 are arranged between the tenons and theferrules.

The construction in Fig. '7 combines the features of Figs. 5 and 6 inthat the ferrules are threaded both to the tenons and to the shroudstrip; however. the external threaded connection 34 is preferablycylindrical instead of being conical. as in Fig. 5.

In Fig. 8. the ferrules are cylindrical. as in Fig. 4. but. instead ofhaving outer ribs or flanges forming parts of the compressiveconnections between the tenons and the shroud strips, external threadedconnections 34 serve the purpose thereof.

Fig. 9 differs from the preceding constructions in that the blade tenonsand the ferrules are of a length materially less than the thickness ofthe shroud strip to provide recesses 42 for weld metal 43 autogenouslyconnecting the ferrules, tenons and shroud strip.

To avoid windage losses due to the projecting heads on the tenons. thestructure is modified to eliminate such heads. Aside from the structureof Fig. 9 inherently accomplishing this purpose,

where the weld and shroud strip outer surfaces are flush, those of theremaining views may be modified for this purpose. For example, as shownin Fig. 10, the preferred structure of Figs. 1. 2 and 3 may have theheads 20 removed if the ferrules are chamfered sufiiciently for tenondefor mation adequate for the connections.

While I have shown my invention in several forms, it will be obvious tothose skilled in the art that it is not so limited, but is susceptibleof various other changes and modifications without departing from thespirit thereof, and I desire, therefore, that only such limitationsshall be placed thereupon as are imposed by the prior art or as arespecifically set forth in the appended claims.

WhatI claim is:

1. In" a turbine, a supporting member having an arcuate periphery,blades extending radially from the periphery of said supporting member,tenons extending radially from the free ends of said blades asegmentalshroud ring having openings for said tenonsrsatit'openings beingmaterially larger than the tenons and concentric relative thereto, andmeans forming connections between the tenons and the shroud to hold thelatter in place with respect to the blade and including ferrules fillingthe spaces between the tenons and the walls of the openings.

2. In a turbine, a supporting member having an arcuate periphery, bladesextending radially from the periphery of the supporting member,cylindrical tenons extending radially from the free ends of the blades,a segmental shroud ring having openings for the tenons, said openingsbeing of such size and shape as to provide concentric annular spacesabout the tenons, and means forming connections between the tenons andthe shroud to hold the latter in place with respect to the blades andincluding ferrules filling said spaces.

3. A structure as specified in claim 2, wherein there are heads on thetenons engaging the outer surfaces of the ferrules.

4. In a turbine, a supporting member having an arcuate periphery, bladesextending radially from the periphery of the supporting member,cylindrical tenons extending radially from the free ends of the blades,a segmental shroud ring having outwardly flaring tapered openings forthe tenons, said openings being materially larger than the tenons andconcentric relative thereto, and means forming connections between thetenons and the shroud to hold the latter in place with respect to theblades and including ferrules filling the spaces between the tenons andthe walls of the openings and means for retaining the ferrules on thetenons.

5. A structure as specified in claim 4, wherein inner walls of theferrules are chamfered at their outer ends, and the means for retainingthe ferrules on the tenons includes heads on the tenons filling thespaces provided by the chamfers.

6. In a turbine, a supporting member having an arcuate periphery, bladesextending radially from the periphery of the supporting member,cylindrical tenons extending radially from the outer ends of the blades,a relatively heavy shroud ring having outwardly tapered circularopenings for the tenons, said openings being materially larger than thetenons and concentric relative thereto, and means forming connectionsbetween the tenons and the shroud to hold the latter in place withrespect to the blades and including femiles closely surrounding thetenons and filling the spaces between the latter and the walls of theopenings and having their inner Walls chambered at their outer ends, andmeans for retaining the ferrules on the tenons including heads on thetenons filling the spaces provided by the chamfers and said heads andferrules being flush with the outer surface of the shroud ring.

7. In a turbine, a supporting member having an arcuate periphery, bladesextending radially from the periphery of the supporting member,cylindrical tenons extending radially from the free ends of the blades,a relatively heavy shroud ring having openings for the tenons, saidopenings being materially larger than the latter and concentricallydisposed relative thereto, and means forming connections between thetenons and the shroud to hold the latter in place with respect to theblades and including ferrules having threaded connections with thetenons and filling the spaces between the latter and the walls of theopenings.

8. In a turbine, a support having an-arcuate periphery, blades extendingradially from the periphery of the support, cylindrical peg-likemembersextending radially from the free ends of the blades, a relatively heavyannular shroud member having openings for the peg-like members whichOpenings are materially larger than the latter and are disposedconcentrically relative thereto, and means forming connections betweenthe peg-like members and the shroud to hold the latter in place withrespect to the blades and including ferrules associated with the peglikemembers and the shroud member and filling the spaces therebetween, eachferrule having a threaded connection with at least one of the memberswith which it is associated.

9. In a turbine, a supporting member having an arcuate periphery, bladesextending radially from the periphery 01' the supporting member,cylindrical tenons extending radially from the outer ends of the blades,a relatively heavy shroud ring having openings for the tenons whichopenings are of materially greater diameter than the latter and areconcentrically disposed relative thereto, and means forming connectionsbetween the tenons and the shroud to hold the latter in place withrespect to the blades and including ferrules filling the spaces betweenthe tenons and the walls of the openings and having threaded connectionswith the latter.

10. In a turbine, a supporting member having an annular periphery,blades extending radially from the periphery of the supporting member,cylindrical tenons extending radially from the free ends of the blades,a relatively heavy shroud strip having openings for the tenons whichopenings are materially larger than the latter and are concentricallydisposed relative thereto, and means forming connections between thetenons and the shroud to hold the latter in place with respect to theblades and including cylindrical ferrules surrounding the tenons andfilling the spaces between the latter and the walls of the openings,annular shoulders at the outer ends of the ferrules overlying andcontacting the outer surface of the shroud ring, and heads on the tenonsretaining the ferrules thereon.

JOSEPH C. BOHAN.

r ri' J J CERTIFICATE OF CORRECTION. Patent No. 2,197,55 April 16, 191m.

of the above numbered patent requiring correction as follows: Page 2,sec- 0nd column, line 5, claim 6, for the word "chambered" read--chamfered--; and that the said Letters Patent should be read with thiscorrection there- Henry Ven Arsdale, (Seal) Acting Commissioner ofPatents.

